Multiple-filament electrodes for electric discharge lamps

ABSTRACT

Electrodes for an electric discharge lamp, such as a &#39;&#39;&#39;&#39;rapid start&#39;&#39;&#39;&#39; fluorescent lamp, comprise a plurality of elongated filaments in close parallel mutual adjacency, preferably touching one another. This reduces the thermal inertia of the electrodes and results in faster filament heating and quicker lamp starting, greater current capacity, and longer life.

United States Paten Lemmers 51 Nov. 11, 1975 [54] MULTIPLE-FILAMENT ELECTRODES FOR 2.125.105 7/1933 Espe 313/343 ELECTRIC DISCHARGE LAMPS 2.233.741 3/1941 Kirsten 313/343 2.283.891 5/1942 Mouromtseff et al. 313/341 Inventor: Eugene Lemmers, Cleveland 2.312.245 2/1943 Flaws. n 313/333 Heights, Ohio 2.337.993 12/1943 C H4111. Jr. et al 315/100 [73] Assignee: General Electric Company,

Schenectady Primary E.\'unziner-Alfred E. Smith [22 i Man 13, 97 Assistant Examiner-Wm. H. Punter Attorney. Agent, or Firm-Norman C. Fulmer; [21] Appl- 450399 Lawrence R. Kempton; Frank L. Neuhauser Related US. Application Data [63] C0ntinuation-in-part of Ser. No. 345,535, March 28.

1973'. abandoned. 57 ABSTRACT [1.5- C]- Electrodes for an electric discharge lamp such as a i 313/345 rapid start fluorescent lamp, comprise a plurality of [5 l l CL" elongat d filament in lose parallel mutual adjacen [58] new M Search 31307313331343 preferably touching one another. This reduces the 313/491- 492 thermal inertia of the electrodes and results in faster filament heating and quicker lamp starting. greater [56] References Clted current capacity, and longer life.

UNITED STATES PATENTS 1.357,?24 11/1920 Randall et al .1. 313/273 5 Claims; 3 Drawing Figures U.S. Patent Nov. 11, 1975 MULTIPLE-FILAM'ENT ELECTRODES FOR ELECTRIC DISCHARGE LAMPS The presentapplication'is acontinuation in part of my copendingapplication Ser. No. 345,535 filed Mar. 28, 1973, now abandoned. r 3

BACKGROUND OFTHE INVENTION.

The invention is in" the field of electric discharge lamps, such as fluorescent lamps, and is more particularly directed to filament-type electrodes for us'e'in suchlamps of the rapid start" type which are started by simultaneously applyingoperating voltage across the electrodes and heatingcurrent'th rough the filaments of both electrodes. i

Fluorescent lamps generally comprise a pair of electrodes respectively sealed into the ends of an elongated glass envelopewhich contains a combination of gases at suitable'pressure for-causing an electricd ischarg'e when voltage is appliedacrossthe electrodes. Eachof the lamp electrodescomprises one o more elongated filaments carried by a lead-in wire, arrangeme n'tlj'lfhe filaments are coated with suitable electron emission materials so as tofunct'ion as cathodes, i.e., a source of electrons for current flow in theilanipThe lamp electrodes may also be provided with anode elements, or in some cases, the cathodes may als o function as anodes to receive the discharge electron flow on alte r riate halfcycles of a -c electricalene rgy, w 1 i The required area ofthe electronem it ting cathodes is a function ,of desired current in the electrical discharge in the lamp. For twice as much discharge current, approximately twice as much cathode area is required. For a single cathode, typically comprising an elongated coiled or coiled-coil filament, to double the surface area (withoutincreasing the length) requires quadrupling the cross-section area, and hence weight, of the filament wire. This considerably increases. the thermal mass of the cathode and henceundesirably. increases the time required forthecathode to reach. proper electron-emitting temperature when a .rapid start lamp is started. This slower heatingof thecathode results in damage to the cathode at each starting, particularly in rapid start lamps, because of the discharge starting due to voltage field effect and tearing.

away electrons and also emission material from the cathode before the cathode has reached proper electron-emitting temperature. This reduces the cathode life. Electrodes provided with multiple cathodes help reduce this undesired effect, since the multiple cathodes increase the total cathode electron-emitting area without increasing the thermal mass as much as in the case of a single-filament cathode. US Pat. Nos. 2,337,993 to Hall and Le Gette and 3,448,318 to Campbell and Kershaw disclose multiple filaments arranged in spaced parallelism in a crisscross configuration and in a straight line configuration.

SUMMARY OF THE INVENTION Electrodes for an electric discharge lamp, such as at.

rapid start fluorescent lamp, comprise a plurality of elongated filaments in close parallel mutual adjacency, preferably touching one another. This reduces the thermal inertia of the electrodes and results in faster starting, greater current capacity, and longer life. The arrangement also increases the amount of electronemitting material that can be coated onto, and held by, the filaments.

I ui'na co ntai n mercury and argon or other suitable fill one another.

'2 BRIEF D E sciim T o QFTHEIDRAWING FIG/l is a side view of a fluorescent lampconstructed in accordance with a preferred embodiment of the inventionJintriorconstruction details being'shown in dashed lines; i e I FIGI-Z is a perspective view o f 'one of the two identical electrodes used in the lamp" of FIG; 1;: and

FIG. 3 is a top View ofthe electrode of FIG. 2 in a modified form with adjacent filament coils touching DESCRIPTION OF THE PREFERRED EMBODIMENTS Thelamp shown in FIG. 1 comprises an elongated tub'ula'r glass bulb 11 having acoating of phosphor material 12 on the innerlsurface thereof. A pair of electrodes l3, 14 are sealed at the ends of the bulb, respecand 17b which are sealed through glass stems l8 and a i'e'electrical ly connected to connector pins 21 and 22 carried by'jbase'cap arrangements 23 and 24 respecjaterial for sustaining an electric discharge between the electrodes 13 and 14.

shown in FIG. 2, each of the electrode assemblies 1 3 jan d l 4 coinprises pairof lead-in support wires 17a and 1755mm through aglass stem 18, as has been de- E scribed above. An exhaust tubulation, 1 9'is shown, for

use in -evzi c z uati ng air from'the bulb II and applying suitable fill gas orgases' into 'the'bulbduring manufacture of the lamp,after which the tubulation l 9 i s sealed off. A plurality of elongated filaments 26, 27, 28, which may be o f the coiled, coiled-coil, or other suitable. type substantially parallel tothe flare: 2? of the stem 18, and are heldin placeby the lead wlires lTl'a and 17b being bent to crimp into and againstthe filaments 26 27, and 28 near the ends thereof, as shown. More specifically, and as shown in FIG. 2, each of the support wires 17a and 17b is shaped to provide a U-shaped segment positioned so that the legs thereof extend along the row of filaments respectively above and below and in clamping engagement with all of the filaments, the two U- shaped clamping segments being respectively near the ends of the row of filaments. If desired, the ends of the lead wires 17a and 17b, after being formed to crimp and hold the filaments 26, 27, and 28, may be extended and shaped to form anode electrodes, as indicated by numerals 31 and 32. After the filaments 26, 27, and 28 are attached to the lead-in wires 17a and 17b, they are dipped into an electron emission mixture, which may be of any well-known composition and which dries to form a continuous unitary electron-emitting coating 33 over and around all of the filaments.

To achieve the objectives of the invention, the spacing between mutually adjacent filaments should be no greater than the diameter of each of the filaments. Normally, all of the filaments will have the same diameter and will be identical in other respects so that when heating current is applied to them the current will be equally distributed among the parallel-connected filaments. lf for some reason mutually adjacent filaments are employed which have differing diameters, they should be no farther apart than the diameter of the smaller diameter filament.

In the preferred embodiment of H6. 3, the filaments are close together so that mutually adjacent filaments 26, 27 and 27, 28 touch one another at a plurality of places along the lengths thereof.

When the electrode arrangement of the invention, as shown in FIG. 2, is employed in an electric discharge lamp,-and especially in a fluorescent lamp of the preheat or rapid start type of lamp in which heating current is fed through the filaments,-it is found that the group of filaments will heat up to proper electronemitting operating temperature much faster than prior art electrode structures to support a given are current, because the close adjacency of the filaments to one another causes the heating of each of them to help heat one or more of the other filaments. This faster heating of the filaments to proper selectron-emitting temperature permits faster starting of the preheat type of lamp and results in longer life in a rapid start type of lamp in which operating electron-emitting is applied across the electrodes 13 and 14 simultaneously with application of heating current to the filaments of each of the electrodes. By thus reducing the thermal mass of the filament arrangement by utilizing several filaments, and providing faster war'm-up due to the close adjacency of the multiple filaments, there is less time during each start-up of the lamp in which the electric field intensity between the electrodes in the lamp can tear or pull" away electrons, and also emission material, from the cathode or filaments before they have reached proper electron-emitting temperature. Also, the close parallel adjacency of the multiple filaments increases the amount of electron-emitting material that can be coated onto, and held by, the cathode structure. Also,

the close adjacency causes the cathode-emitting area to be shared proportionally among the several cathodes, thus resulting in a unitary electron-emitting configuration While preferred embodiments of the invention have 'been'shown and described, various other embodiments and modifications thereof will become apparent to persons skilled in the art and will fall within the scope of the invention as defined in the following claims.

What I claim as new and desire to secure by letters patent of the United States is:

1. An electrode for an electric discharge lamp, comprising at least three helically coiled elongated electrical filaments arranged side by side in a row lying in a plane, the mutually adjacent ones of said filaments being positioned in close parallel mutual adjacency, the spacing between mutually adjacent filaments being no greater than the diameter of either of them, electronemitting material coated on said filaments, and a pair of lead-in electrical conductors respectively at the ends of the plurality of filaments and connecting them in electrical parallel.

2. An electrode as claimed in claim 1 in which mutually adjacent filaments of said electrode touch one another at a plurality of places along the lengths thereof.

3. An electrode as claimed in claim 1 in which said electron-emitting material is coated over said plurality of filaments and forms a continuous unitary coating over and around all of the filaments.

4. An electrode as claimed in claim 1 including a stem and a pair of lead-in support wires extending from said stem, each of said wires being shaped to provide a U-shaped segment, one of said U-shaped segments being positioned so that the legs thereof extend along said row respectively above and below and in clamping engagement with all of said filaments near the ends thereof at one side of said row, and the other one of said U-shaped segments being similarly positioned in clamping engagement with all of said filaments near the other ends thereof at the other side of said row, whereby said U-shaped segments simultaneously support and provide electrical connections to said plurality of filaments.

5. An electrode as claimed in claim 4 in which at least one of said legs of the U-shaped segments extends from said clamping engagement with the filaments and into space near the filaments so as to function as an anode member of said electrode. 

1. An electrode for an electric discharge lamp, comprising at least three helically coiled elongated electrical filaments arranged side by side in a row lying in a plane, the mutually adjacent ones of said filaments being positioned in close parallel mutual adjacency, the spacing between mutually adjacent filaments being no greater than the diameter of either of them, electron-emitting material coated on said filaments, and a pair of lead-in electrical conductors respectively at the ends of the plurality of filaments and connecting them in electrical parallel.
 2. An electrode as claimed in claim 1 in which mutually adjacent filaments of said electrode touch one another at a plurality of places along the lengths thereof.
 3. An electrode as claimed in claim 1 in which said electron-emitting material is coated over said plurality of filaments and forms a continuous unitary coating over and around all of the filaments.
 4. An electrode as claimed in claim 1 including a stem and a pair of lead-in support wires extending from said stem, each of said wires being shaped to provide a U-shaped segment, one of said U-shaped segments being positioned so that the legs thereof extend along said row respectively above and below and in clamping engagement with all of said filaments near the ends thereof at one side of said row, and the other one of said U-shaped segments being similarly positioned in clamping engagement with all of said filaments near the other ends thereof at the other side of said row, whereby said U-shaped segments simultaneously support and provide electrical connections to said plurality of filaments.
 5. An electrode as claimed In claim 4 in which at least one of said legs of the U-shaped segments extends from said clamping engagement with the filaments and into space near the filaments so as to function as an anode member of said electrode. 